6hrslave - B.3 PROGRAM .SLAVE

Users » manujose » Code » 6hrslave

B.3 PROGRAM .SLAVE

pt-sem.h@1:695db1757630, 2010-12-14 (annotated)

Committer:: manujose
Date:: Tue Dec 14 23:26:42 2010 +0000
Revision:: 1:695db1757630
Parent:: 0:9092ea8d9a6c

Who changed what in which revision?

User	Revision	Line number	New contents of line
manujose	0:9092ea8d9a6c	1	/*
manujose	0:9092ea8d9a6c	2	* Copyright (c) 2004, Swedish Institute of Computer Science.
manujose	0:9092ea8d9a6c	3	* All rights reserved.
manujose	0:9092ea8d9a6c	4	*
manujose	0:9092ea8d9a6c	5	* Redistribution and use in source and binary forms, with or without
manujose	0:9092ea8d9a6c	6	* modification, are permitted provided that the following conditions
manujose	0:9092ea8d9a6c	7	* are met:
manujose	0:9092ea8d9a6c	8	* 1. Redistributions of source code must retain the above copyright
manujose	0:9092ea8d9a6c	9	* notice, this list of conditions and the following disclaimer.
manujose	0:9092ea8d9a6c	10	* 2. Redistributions in binary form must reproduce the above copyright
manujose	0:9092ea8d9a6c	11	* notice, this list of conditions and the following disclaimer in the
manujose	0:9092ea8d9a6c	12	* documentation and/or other materials provided with the distribution.
manujose	0:9092ea8d9a6c	13	* 3. Neither the name of the Institute nor the names of its contributors
manujose	0:9092ea8d9a6c	14	* may be used to endorse or promote products derived from this software
manujose	0:9092ea8d9a6c	15	* without specific prior written permission.
manujose	0:9092ea8d9a6c	16	*
manujose	0:9092ea8d9a6c	17	* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
manujose	0:9092ea8d9a6c	18	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
manujose	0:9092ea8d9a6c	19	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
manujose	0:9092ea8d9a6c	20	* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
manujose	0:9092ea8d9a6c	21	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
manujose	0:9092ea8d9a6c	22	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
manujose	0:9092ea8d9a6c	23	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
manujose	0:9092ea8d9a6c	24	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
manujose	0:9092ea8d9a6c	25	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
manujose	0:9092ea8d9a6c	26	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
manujose	0:9092ea8d9a6c	27	* SUCH DAMAGE.
manujose	0:9092ea8d9a6c	28	*
manujose	0:9092ea8d9a6c	29	* This file is part of the protothreads library.
manujose	0:9092ea8d9a6c	30	*
manujose	0:9092ea8d9a6c	31	* Author: Adam Dunkels <adam@sics.se>
manujose	0:9092ea8d9a6c	32	*
manujose	0:9092ea8d9a6c	33	* $Id: pt-sem.h,v 1.2 2005/02/24 10:36:59 adam Exp $
manujose	0:9092ea8d9a6c	34	*/
manujose	0:9092ea8d9a6c	35
manujose	0:9092ea8d9a6c	36	/**
manujose	0:9092ea8d9a6c	37	* \addtogroup pt
manujose	0:9092ea8d9a6c	38	* @{
manujose	0:9092ea8d9a6c	39	*/
manujose	0:9092ea8d9a6c	40
manujose	0:9092ea8d9a6c	41	/**
manujose	0:9092ea8d9a6c	42	* \defgroup ptsem Protothread semaphores
manujose	0:9092ea8d9a6c	43	* @{
manujose	0:9092ea8d9a6c	44	*
manujose	0:9092ea8d9a6c	45	* This module implements counting semaphores on top of
manujose	0:9092ea8d9a6c	46	* protothreads. Semaphores are a synchronization primitive that
manujose	0:9092ea8d9a6c	47	* provide two operations: "wait" and "signal". The "wait" operation
manujose	0:9092ea8d9a6c	48	* checks the semaphore counter and blocks the thread if the counter
manujose	0:9092ea8d9a6c	49	* is zero. The "signal" operation increases the semaphore counter but
manujose	0:9092ea8d9a6c	50	* does not block. If another thread has blocked waiting for the
manujose	0:9092ea8d9a6c	51	* semaphore that is signalled, the blocked thread will become
manujose	0:9092ea8d9a6c	52	* runnable again.
manujose	0:9092ea8d9a6c	53	*
manujose	0:9092ea8d9a6c	54	* Semaphores can be used to implement other, more structured,
manujose	0:9092ea8d9a6c	55	* synchronization primitives such as monitors and message
manujose	0:9092ea8d9a6c	56	* queues/bounded buffers (see below).
manujose	0:9092ea8d9a6c	57	*
manujose	0:9092ea8d9a6c	58	* The following example shows how the producer-consumer problem, also
manujose	0:9092ea8d9a6c	59	* known as the bounded buffer problem, can be solved using
manujose	0:9092ea8d9a6c	60	* protothreads and semaphores. Notes on the program follow after the
manujose	0:9092ea8d9a6c	61	* example.
manujose	0:9092ea8d9a6c	62	*
manujose	0:9092ea8d9a6c	63	\code
manujose	0:9092ea8d9a6c	64	#include "pt-sem.h"
manujose	0:9092ea8d9a6c	65
manujose	0:9092ea8d9a6c	66	#define NUM_ITEMS 32
manujose	0:9092ea8d9a6c	67	#define BUFSIZE 8
manujose	0:9092ea8d9a6c	68
manujose	0:9092ea8d9a6c	69	static struct pt_sem mutex, full, empty;
manujose	0:9092ea8d9a6c	70
manujose	0:9092ea8d9a6c	71	PT_THREAD(producer(struct pt *pt))
manujose	0:9092ea8d9a6c	72	{
manujose	0:9092ea8d9a6c	73	static int produced;
manujose	0:9092ea8d9a6c	74
manujose	0:9092ea8d9a6c	75	PT_BEGIN(pt);
manujose	0:9092ea8d9a6c	76
manujose	0:9092ea8d9a6c	77	for(produced = 0; produced < NUM_ITEMS; ++produced) {
manujose	0:9092ea8d9a6c	78
manujose	0:9092ea8d9a6c	79	PT_SEM_WAIT(pt, &full);
manujose	0:9092ea8d9a6c	80
manujose	0:9092ea8d9a6c	81	PT_SEM_WAIT(pt, &mutex);
manujose	0:9092ea8d9a6c	82	add_to_buffer(produce_item());
manujose	0:9092ea8d9a6c	83	PT_SEM_SIGNAL(pt, &mutex);
manujose	0:9092ea8d9a6c	84
manujose	0:9092ea8d9a6c	85	PT_SEM_SIGNAL(pt, &empty);
manujose	0:9092ea8d9a6c	86	}
manujose	0:9092ea8d9a6c	87
manujose	0:9092ea8d9a6c	88	PT_END(pt);
manujose	0:9092ea8d9a6c	89	}
manujose	0:9092ea8d9a6c	90
manujose	0:9092ea8d9a6c	91	PT_THREAD(consumer(struct pt *pt))
manujose	0:9092ea8d9a6c	92	{
manujose	0:9092ea8d9a6c	93	static int consumed;
manujose	0:9092ea8d9a6c	94
manujose	0:9092ea8d9a6c	95	PT_BEGIN(pt);
manujose	0:9092ea8d9a6c	96
manujose	0:9092ea8d9a6c	97	for(consumed = 0; consumed < NUM_ITEMS; ++consumed) {
manujose	0:9092ea8d9a6c	98
manujose	0:9092ea8d9a6c	99	PT_SEM_WAIT(pt, &empty);
manujose	0:9092ea8d9a6c	100
manujose	0:9092ea8d9a6c	101	PT_SEM_WAIT(pt, &mutex);
manujose	0:9092ea8d9a6c	102	consume_item(get_from_buffer());
manujose	0:9092ea8d9a6c	103	PT_SEM_SIGNAL(pt, &mutex);
manujose	0:9092ea8d9a6c	104
manujose	0:9092ea8d9a6c	105	PT_SEM_SIGNAL(pt, &full);
manujose	0:9092ea8d9a6c	106	}
manujose	0:9092ea8d9a6c	107
manujose	0:9092ea8d9a6c	108	PT_END(pt);
manujose	0:9092ea8d9a6c	109	}
manujose	0:9092ea8d9a6c	110
manujose	0:9092ea8d9a6c	111	PT_THREAD(driver_thread(struct pt *pt))
manujose	0:9092ea8d9a6c	112	{
manujose	0:9092ea8d9a6c	113	static struct pt pt_producer, pt_consumer;
manujose	0:9092ea8d9a6c	114
manujose	0:9092ea8d9a6c	115	PT_BEGIN(pt);
manujose	0:9092ea8d9a6c	116
manujose	0:9092ea8d9a6c	117	PT_SEM_INIT(&empty, 0);
manujose	0:9092ea8d9a6c	118	PT_SEM_INIT(&full, BUFSIZE);
manujose	0:9092ea8d9a6c	119	PT_SEM_INIT(&mutex, 1);
manujose	0:9092ea8d9a6c	120
manujose	0:9092ea8d9a6c	121	PT_INIT(&pt_producer);
manujose	0:9092ea8d9a6c	122	PT_INIT(&pt_consumer);
manujose	0:9092ea8d9a6c	123
manujose	0:9092ea8d9a6c	124	PT_WAIT_THREAD(pt, producer(&pt_producer) &
manujose	0:9092ea8d9a6c	125	consumer(&pt_consumer));
manujose	0:9092ea8d9a6c	126
manujose	0:9092ea8d9a6c	127	PT_END(pt);
manujose	0:9092ea8d9a6c	128	}
manujose	0:9092ea8d9a6c	129	\endcode
manujose	0:9092ea8d9a6c	130	*
manujose	0:9092ea8d9a6c	131	* The program uses three protothreads: one protothread that
manujose	0:9092ea8d9a6c	132	* implements the consumer, one thread that implements the producer,
manujose	0:9092ea8d9a6c	133	* and one protothread that drives the two other protothreads. The
manujose	0:9092ea8d9a6c	134	* program uses three semaphores: "full", "empty" and "mutex". The
manujose	0:9092ea8d9a6c	135	* "mutex" semaphore is used to provide mutual exclusion for the
manujose	0:9092ea8d9a6c	136	* buffer, the "empty" semaphore is used to block the consumer is the
manujose	0:9092ea8d9a6c	137	* buffer is empty, and the "full" semaphore is used to block the
manujose	0:9092ea8d9a6c	138	* producer is the buffer is full.
manujose	0:9092ea8d9a6c	139	*
manujose	0:9092ea8d9a6c	140	* The "driver_thread" holds two protothread state variables,
manujose	0:9092ea8d9a6c	141	* "pt_producer" and "pt_consumer". It is important to note that both
manujose	0:9092ea8d9a6c	142	* these variables are declared as <i>static</i>. If the static
manujose	0:9092ea8d9a6c	143	* keyword is not used, both variables are stored on the stack. Since
manujose	0:9092ea8d9a6c	144	* protothreads do not store the stack, these variables may be
manujose	0:9092ea8d9a6c	145	* overwritten during a protothread wait operation. Similarly, both
manujose	0:9092ea8d9a6c	146	* the "consumer" and "producer" protothreads declare their local
manujose	0:9092ea8d9a6c	147	* variables as static, to avoid them being stored on the stack.
manujose	0:9092ea8d9a6c	148	*
manujose	0:9092ea8d9a6c	149	*
manujose	0:9092ea8d9a6c	150	*/
manujose	0:9092ea8d9a6c	151
manujose	0:9092ea8d9a6c	152	/**
manujose	0:9092ea8d9a6c	153	* \file
manujose	0:9092ea8d9a6c	154	* Couting semaphores implemented on protothreads
manujose	0:9092ea8d9a6c	155	* \author
manujose	0:9092ea8d9a6c	156	* Adam Dunkels <adam@sics.se>
manujose	0:9092ea8d9a6c	157	*
manujose	0:9092ea8d9a6c	158	*/
manujose	0:9092ea8d9a6c	159
manujose	0:9092ea8d9a6c	160	#ifndef __PT_SEM_H__
manujose	0:9092ea8d9a6c	161	#define __PT_SEM_H__
manujose	0:9092ea8d9a6c	162
manujose	0:9092ea8d9a6c	163	#include "pt.h"
manujose	0:9092ea8d9a6c	164
manujose	0:9092ea8d9a6c	165	struct pt_sem {
manujose	0:9092ea8d9a6c	166	unsigned int count;
manujose	0:9092ea8d9a6c	167	};
manujose	0:9092ea8d9a6c	168
manujose	0:9092ea8d9a6c	169	/**
manujose	0:9092ea8d9a6c	170	* Initialize a semaphore
manujose	0:9092ea8d9a6c	171	*
manujose	0:9092ea8d9a6c	172	* This macro initializes a semaphore with a value for the
manujose	0:9092ea8d9a6c	173	* counter. Internally, the semaphores use an "unsigned int" to
manujose	0:9092ea8d9a6c	174	* represent the counter, and therefore the "count" argument should be
manujose	0:9092ea8d9a6c	175	* within range of an unsigned int.
manujose	0:9092ea8d9a6c	176	*
manujose	0:9092ea8d9a6c	177	* \param s (struct pt_sem *) A pointer to the pt_sem struct
manujose	0:9092ea8d9a6c	178	* representing the semaphore
manujose	0:9092ea8d9a6c	179	*
manujose	0:9092ea8d9a6c	180	* \param c (unsigned int) The initial count of the semaphore.
manujose	0:9092ea8d9a6c	181	* \hideinitializer
manujose	0:9092ea8d9a6c	182	*/
manujose	0:9092ea8d9a6c	183	#define PT_SEM_INIT(s, c) (s)->count = c
manujose	0:9092ea8d9a6c	184
manujose	0:9092ea8d9a6c	185	/**
manujose	0:9092ea8d9a6c	186	* Wait for a semaphore
manujose	0:9092ea8d9a6c	187	*
manujose	0:9092ea8d9a6c	188	* This macro carries out the "wait" operation on the semaphore. The
manujose	0:9092ea8d9a6c	189	* wait operation causes the protothread to block while the counter is
manujose	0:9092ea8d9a6c	190	* zero. When the counter reaches a value larger than zero, the
manujose	0:9092ea8d9a6c	191	* protothread will continue.
manujose	0:9092ea8d9a6c	192	*
manujose	0:9092ea8d9a6c	193	* \param pt (struct pt *) A pointer to the protothread (struct pt) in
manujose	0:9092ea8d9a6c	194	* which the operation is executed.
manujose	0:9092ea8d9a6c	195	*
manujose	0:9092ea8d9a6c	196	* \param s (struct pt_sem *) A pointer to the pt_sem struct
manujose	0:9092ea8d9a6c	197	* representing the semaphore
manujose	0:9092ea8d9a6c	198	*
manujose	0:9092ea8d9a6c	199	* \hideinitializer
manujose	0:9092ea8d9a6c	200	*/
manujose	0:9092ea8d9a6c	201	#define PT_SEM_WAIT(pt, s) \
manujose	0:9092ea8d9a6c	202	do { \
manujose	0:9092ea8d9a6c	203	PT_WAIT_UNTIL(pt, (s)->count > 0); \
manujose	0:9092ea8d9a6c	204	--(s)->count; \
manujose	0:9092ea8d9a6c	205	} while(0)
manujose	0:9092ea8d9a6c	206
manujose	0:9092ea8d9a6c	207	/**
manujose	0:9092ea8d9a6c	208	* Signal a semaphore
manujose	0:9092ea8d9a6c	209	*
manujose	0:9092ea8d9a6c	210	* This macro carries out the "signal" operation on the semaphore. The
manujose	0:9092ea8d9a6c	211	* signal operation increments the counter inside the semaphore, which
manujose	0:9092ea8d9a6c	212	* eventually will cause waiting protothreads to continue executing.
manujose	0:9092ea8d9a6c	213	*
manujose	0:9092ea8d9a6c	214	* \param pt (struct pt *) A pointer to the protothread (struct pt) in
manujose	0:9092ea8d9a6c	215	* which the operation is executed.
manujose	0:9092ea8d9a6c	216	*
manujose	0:9092ea8d9a6c	217	* \param s (struct pt_sem *) A pointer to the pt_sem struct
manujose	0:9092ea8d9a6c	218	* representing the semaphore
manujose	0:9092ea8d9a6c	219	*
manujose	0:9092ea8d9a6c	220	* \hideinitializer
manujose	0:9092ea8d9a6c	221	*/
manujose	0:9092ea8d9a6c	222	#define PT_SEM_SIGNAL(pt, s) ++(s)->count
manujose	0:9092ea8d9a6c	223
manujose	0:9092ea8d9a6c	224	#endif /* __PT_SEM_H__ */
manujose	0:9092ea8d9a6c	225
manujose	0:9092ea8d9a6c	226	/** @} */
manujose	0:9092ea8d9a6c	227	/** @} */
manujose	0:9092ea8d9a6c	228

Repository toolbox

Export to desktop IDE

Build repository

Repository details

Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	04 Dec 2010
Imports:	7
Forks:	0
Commits:	2
Dependents:	0
Dependencies:	1
Followers:	1

pt-sem.h@1:695db1757630, 2010-12-14 (annotated)

Who changed what in which revision?

Repository toolbox

Repository details

Important Information for this Arm website

Access Warning